JP2000277869A - Modulator integrated type semiconductor laser and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modulator integrated type semiconductor laser with improved frequency characteristic, by reducing the effects of field variation due to the modulation signal applied to a modulator. SOLUTION: An active layer 16, an optical waveguide layer 32 with a bulk structure with a band gap energy larger than that of the active layer 16, and an optical absorption layer 40 with bulk structure with a band gap energy larger than that of the active layer 16 and smaller than the optical waveguide layer 32 are formed continuously in waveguides 20, 36 and 44. A clad layer 22 which includes a diffraction grating 24 is formed on or under the waveguides 20, 36, and 44 to constitute this laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulator-integrated semiconductor laser device used for optical communication and a method of manufacturing the same, and more particularly, to reducing the influence of electric field fluctuation due to a modulation signal applied to the modulator. The present invention relates to a modulator integrated semiconductor laser device having improved frequency characteristics and a method of manufacturing the same.

[0002]

2. Description of the Related Art To spread a public communication network using an optical fiber, it is important to improve the performance of a semiconductor laser and to improve the yield in order to manufacture the semiconductor laser at low cost. In particular, in order to improve the performance of a semiconductor laser, high-speed modulation of laser light is an essential requirement to cope with an increase in the amount of information. In this high-speed modulation of laser light, a semiconductor laser is usually oscillated at a constant intensity and the amount of transmitted light is turned on in order to reduce fluctuations in wavelength during modulation and enable long-distance transmission. An external modulation method for performing modulation by passing through a modulator that can be turned off is employed.

In this external modulation method, there is a problem that optical coupling between the modulator and the semiconductor laser is difficult and the number of components is large, so that the cost is high. A modulator-integrated semiconductor laser in which a device is monolithically integrated is being developed. In this modulator integrated semiconductor laser,
The common electrode is grounded, current is injected with a forward bias in the semiconductor laser, and a modulation signal with a reverse bias is applied to the modulator side. Therefore, the configuration of the separation region provided between the semiconductor laser and the modulator becomes important. In a semiconductor modulator, when the light absorption layer of the modulator is formed with a multiple quantum well structure (hereinafter, referred to as MQW), a high extinction ratio (a ratio of the amount of light transmission between on and off) can be obtained at a low operating voltage. Therefore, in high-speed transmission, a light absorption layer of MQW is usually used.

FIG. 27 is a partially cutaway perspective view of a conventional modulator integrated semiconductor laser (hereinafter referred to as a laser with modulator). FIG. 28 shows XXVIII-XXVII of FIG.
It is sectional drawing of I section. 27 and 28, 20
Reference numeral 1 denotes a laser with a modulator, D denotes a separation / modulation unit including a separation unit and a modulator unit, and C denotes a laser unit.

In FIGS. 27 and 28, reference numeral 202 denotes n-
InP substrate 204, n-InGaAsP laser n
Side light confinement layer, 206 is an active layer of InGaAsP-MQW, 208 is a laser p side light confinement layer of p-InGaAsP, laser n side light confinement layer 204, active layer 206 and laser p side light confinement layer The laser waveguide 207 is constituted by 208. 210 is a first cladding layer of p-InP, 212 is p-InP
A diffraction grating of -InGaAsP, 214 is a second cladding layer of p-InP, and 216 is a contact layer of p ⁺ -InGaAs. Here, "n-" represents "n-type" and "p-" represents "p-type". The same applies to the following.

Reference numeral 218 denotes an n-InGaAsP separation / modulation unit n-side optical confinement layer, and 220 denotes an InGa of the separation / modulation unit D.
AsP-MQW light absorbing layer, light absorbing layer 2 in modulator region
20a and the optical waveguide layer 220b in the isolation region.
Reference numeral 222 denotes a p-side light confinement layer of the p-InGaAsP separation / modulation unit. The separation / modulation unit waveguide 221 is constituted by the separation / modulation unit n-side light confinement layer 218, the light absorption layer 220, and the separation / modulation unit p-side light confinement layer.

224 is a first buried layer of Fe-doped InP,
226 is an n-InP hole trap layer, 228 is Fe
The first buried layer 224, the hole trapping layer 226, and the second buried layer 228 are also formed on both side surfaces of the ridge-shaped laser waveguide 207 and the separation / modulator waveguide 221 in the second buried layer of doped InP. These constitute a current blocking layer, and constitute a window structure 229 on the emission end face side.
230 is an insulating film of SiO2, 231 is a separation groove for separating the laser portion C and the modulator region, 232 is a surface deposited electrode of Ti / Au, 234 is a p-side laser electrode of an Au plating layer,
236 is a p-side modulator electrode of the Au plating layer, 238 is a vapor deposition electrode, and 240 is a common electrode. The arrow 242 indicates the emission direction of the laser light.

A conventional laser with a modulator is manufactured as follows. First, n-InGaAs as a laser n-side optical confinement layer 204 is formed on a substrate 202 by MOCVD.
InGaAsP-MQW as sP layer and active layer 206
Layer, p-InGaAs as laser p-side optical confinement layer 208
sP layer, p-InP layer as first cladding layer 210,
The p-InGaAsP layers forming the diffraction grating 212 are sequentially stacked by crystal growth.

Next, in order to form the diffraction grating 212, p
-The InGaAsP layer is etched into a lattice shape by using the interference exposure method to form the diffraction grating 212. Thereafter, the entire surface is buried with a p-InP layer serving as the first cladding layer 210. P-InP as the first cladding layer 210
A dielectric film such as SiO2 or SiN is formed on the layer, and the dielectric film is etched such that a stripe-shaped dielectric film for forming a laser waveguide including the diffraction grating 212 remains. Using the dielectric film described above as a mask, the lamination in the region including the separation / modulator portion D is etched until the substrate 202 is exposed.

Next, while the striped dielectric film is left, an n-InGaAsP layer serving as the n-side light confinement layer 218 for the separation / modulation section and the light absorption layer 220 of the separation / modulation section D are formed by MOCVD. InGaAsP-MQW as
Layer, p-I as the p-side optical confinement layer 222 in the separation / modulation unit
An nGaAsP layer and a p-InP layer as the first cladding layer 210 are formed. Thereafter, the striped dielectric film is removed, a dielectric film such as SiO2 or SiN is formed again, and then separated and modulated by etching to form waveguides for the separation and modulator section D and the laser section C. A stripe-shaped dielectric film is formed so as to overlap with the cavity portion D and the laser portion C, and wet etching using HBr is performed using the stripe-shaped dielectric film as a mask until the substrate 202 is exposed, thereby forming a ridge of the waveguide. I do. At this time, when the window structure 229 is formed, a striped dielectric film is formed so that the emission end face side can be removed by etching.

Next, Fe-doped InP is used as the first buried layer 224 with the stripe-shaped dielectric film left.
Layer, an n-InP layer as a hole trap layer 226 and an Fe-doped InP layer as a second buried layer 228
The crystal grows by the D method. Thereafter, the stripe-shaped dielectric film is removed, and a p-InP layer serving as a second cladding layer 214 and a contact layer 21 are entirely formed by MOCVD.
A p ⁺ -InGaAs layer 6 is crystal-grown.

Next, a part of the contact layer 216 corresponding to the separation region and a part of the upper surface of the second cladding layer 214 are removed by etching to form a separation groove 231.
Thereafter, an insulating film 230 is formed on the entire surface by sputtering, and then the insulating film 230 in the modulator region and the electrode contact portion of the laser unit C is removed. Next, the surface deposition electrode 2
32 Ti / Au films and Au plating layers are formed. Thereafter, after grinding the back surface of the substrate 202 until the substrate thickness becomes about 100 μm, AuGe /
A Ni / Ti / Pt / Ti / Pt / Au film is formed by vapor deposition, and an Au plating layer is patterned by plating to form a common electrode 240.

The laser with modulator 2 configured as described above
01, a forward bias voltage is applied between the laser electrode 234 and the common electrode 240 to inject a current into the active layer 206, and the laser light emitted by the laser section C is separated by the separation / modulation section waveguide 221. It is led to the modulator section D, and the modulator electrode 2
A modulation signal of a reverse bias voltage is applied between the common electrode 240 and the common electrode 240, and an electric field corresponding to the modulation signal is applied to the light absorbing layer 220.
When applied to a, the light is modulated under a high extinction ratio by the quantum confined Stark effect, and the high-speed modulated laser light 242 is emitted.

[0014]

The conventional laser 201 with a modulator is configured as described above. The p-side laser electrode 234 and the p-side modulator electrode 236 are provided in the separation groove 231 and the separation groove 231. The laser light 242 is prevented from causing a wavelength variation by being separated by the insulating film 230. However, the light absorbing layer 220a of the modulator has M
Since it is composed of QW, it has the advantage that the extinction ratio is high at a low voltage, but the refractive index is liable to fluctuate under the influence of the electric field fluctuation due to the modulation signal, and the wavelength fluctuation due to the refractive index change is not necessarily reduced. Was. When the wavelength fluctuation is large, the transmission distance cannot be made long.

The laser section C and the separation / modulation section D are arranged via a bonding surface, and the separation / modulation section D is formed by regrowth. That is, the separating / modulating unit D is formed by a single butt-joint method, and has a configuration having a uniform band gap energy. When operating such a semiconductor laser 201 with a modulator, a modulation signal is applied between the modulator electrode 236 and the common electrode 240. The electric field generated by the modulation signal is generated not only between the modulator electrode 236 and the common electrode 240 immediately below the modulator electrode 236 but also between the modulator electrode 236 and the common electrode 240 on the laser unit C side. An electric field is also generated in a portion of the separation / modulation unit waveguide 221 immediately below the separation groove 231.

As described above, since the optical waveguide layer 220b and the light absorbing layer 220a are formed by one regrowth by the butt joint method, they have a structure having a uniform band gap energy. Therefore, not only the light absorbing layer 220a immediately below the modulator electrode 236 absorbs light due to the electric field due to the modulation signal, but also the separation groove 2
Due to the slight electric field applied to the waveguide region just below 31,
Light absorption also occurs in the optical waveguide layer 220b, which causes a disadvantage that the optical waveguide layer 220b operates as a light absorption layer. Optical waveguide layer 220
When b operates as a light absorbing layer, the optical waveguide layer 220
Since the electric field applied to b is smaller than the electric field applied to the light absorption layer 220a, the depletion layer at the pn junction portion of the optical waveguide layer 220b does not spread widely, so that the junction capacitance becomes large.
With respect to the frequency of the modulation signal, light absorption is large in a low frequency region and small in a high frequency region. For this reason, the entire frequency characteristic may not be flat but may be distorted in a waveform (similar).

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to provide a modulator integrated type semiconductor laser device in which a semiconductor laser and a modulator are integrated. An object of the present invention is to provide a modulator-integrated semiconductor laser device having improved frequency characteristics by reducing the influence of electric field fluctuation due to a modulation signal.

A second object of the present invention is to make the modulator a bulk structure to reduce the variation of the absorption coefficient that changes due to the electric field of the modulation signal, reduce the change in the refractive index due to the absorption coefficient change, and reduce the distance between the semiconductor laser and the modulator. Provided is a modulator integrated semiconductor laser device having good frequency characteristics and high output by reducing the absorption of light in the optical waveguide layer due to a leakage electric field by making the optical waveguide layer of the isolation region interposed in the bulk structure. That is.

A third object of the present invention is to provide a semiconductor laser, a modulator, and a waveguide in a separation region interposed between these portions, which are continuous through a junction, and that the optical waveguide layer in the separation region has a bulk crystal structure. Accordingly, it is an object of the present invention to provide a modulator-integrated semiconductor laser device having improved frequency characteristics by reducing the influence of electric field fluctuation due to a modulation signal applied to the modulator.

It is a fourth object of the present invention to provide a manufacturing method capable of easily forming a modulator integrated semiconductor laser device having improved frequency characteristics.

As a well-known document in which the band gap wavelength is changed in the laser portion, the separation portion and the modulator portion of the waveguide of the modulator integrated semiconductor laser device, Japanese Patent Application Laid-Open No. 8-335745 is disclosed.
There is an official gazette. This is a modulator integrated semiconductor laser device having a separation portion and a modulator portion formed by the butt joint method, in which the wavelength is shortened by performing ion implantation on the separation portion. Does not disclose that it has a bulk structure, and does not disclose that the separation unit and the modulator are arranged via the joint surface, and thus the configuration is different. Further, in a laser with a modulator, a semiconductor laser portion, a modulator portion and an intermediate portion thereof are formed at a time by selective growth,
Japanese Patent Application Laid-Open No. H7-176827 discloses that the emission wavelength of the semiconductor laser portion is made larger than the emission wavelength of the modulator portion, and the emission wavelength of the transition region corresponding to the middle between these two portions is made smaller than that of the semiconductor laser portion and the modulator portion. Although it is disclosed in the gazette, there is no disclosure that the semiconductor laser unit and the separation unit are joined by a butt joint method,
Further, the active layer, the optical waveguide layer and the light absorbing layer have an MQW structure, and thus have different structures.

[0022]

In a modulator integrated semiconductor laser device according to the present invention, a semiconductor substrate of a first conductivity type and a part of the semiconductor substrate on one main surface are provided. A ridge-shaped first waveguide having an active layer;
A ridge-shaped optical waveguide layer having a bulk optical waveguide layer that is disposed on the semiconductor substrate in the direction in which the first waveguide extends and is continuous with the first waveguide and has a larger band gap energy than the active layer. A second waveguide, which is disposed on the semiconductor substrate continuously with the second waveguide in an extending direction of the second waveguide, and is larger than the band gap energy of the active layer; A ridge-shaped third waveguide having a light absorption layer having a bulk structure smaller than the band gap energy, and a first conductive type semiconductor disposed on the first, second, and third waveguides. A cladding layer,
A ridge-shaped second ridge including a diffraction grating disposed between the first cladding layer or the semiconductor substrate and the first, second, and third waveguides and disposed along the first waveguide. A current blocking layer disposed on the semiconductor substrate on both sides of the first and second cladding layers, the first, second and third waveguides, and an active layer on the first cladding layer. A first electrode disposed opposite the layer, a second electrode separated from the first electrode and disposed on the first cladding layer opposite the light absorbing layer, and a semiconductor; A third electrode disposed on the other main surface of the substrate, and by having this configuration, the effect of electric field fluctuation due to the modulation signal applied to the modulator is reduced, that is, the modulation signal The fluctuation of the absorption coefficient, which changes with the electric field, and the change in the refractive index of the modulator due to the change in the absorption coefficient Both the optical waveguide layer in the isolation region intervening between the semiconductor laser and the modulator in bulk structure,
The frequency characteristics are improved by reducing the absorption of light in the optical waveguide layer due to the leakage electric field.

Further, since the second waveguide is continuous with the first waveguide via the joint surface, the frequency characteristics are improved while the degree of design freedom is kept high.

Further, the third waveguide is made continuous with the second waveguide via the joint surface, and both the optical waveguide layer and the light absorbing layer have a bulk crystal structure. This is to improve the frequency characteristics. Further, both the optical waveguide layer and the light absorption layer have a multi-quantum well structure in which a mixed crystal is formed by disordering, and the degree of the mixed crystal in the optical waveguide layer is higher than that of the absorption layer.
This is to improve the frequency characteristics with a simple configuration. Furthermore, the second waveguide has a thicker waveguide thickness on the side adjacent to the third waveguide than on the side adjacent to the first waveguide, thereby reducing light absorption and improving frequency characteristics. It is what makes it good.

Also, a first conductivity type semiconductor substrate, a ridge-shaped first waveguide provided on a part of one main surface of the semiconductor substrate and having an active layer, A ridge-shaped second waveguide having an optical waveguide layer having a bandgap energy larger than that of the active layer is provided on the semiconductor substrate so as to be continuous with the first waveguide in a direction in which the waveguide extends and via the bonding surface. A waveguide, which is disposed on the semiconductor substrate so as to be continuous with the second waveguide in a direction of extension of the second waveguide via the bonding surface and is larger than the band gap energy of the active layer; Ridge-shaped third waveguide having a light absorption layer of a multiple quantum well structure smaller than the bandgap energy of the first and second conductive semiconductors disposed on the first, second and third waveguides And the first cladding layer Ridge-shaped second cladding layer disposed between the semiconductor layer and the first, second, and third waveguides and including a diffraction grating disposed along the first waveguide. And a first and second cladding layer, a current blocking layer disposed on the semiconductor substrate on both sides of the first, second and third waveguides, and an active layer on the first cladding layer. A first electrode disposed opposite to the first electrode, a second electrode separated from the first electrode and disposed on the first cladding layer opposite to the absorption layer, and a semiconductor substrate; With the third electrode disposed on the other main surface, while reducing light absorption,
The frequency characteristics are improved by reducing the influence of electric field fluctuation due to the modulation signal applied to the modulator.

Further, since the optical waveguide layer has a bulk crystal structure, the effect of electric field fluctuation due to a modulation signal applied to the modulator is reduced while light absorption is reduced, thereby improving the frequency characteristics. .

Further, since the optical waveguide layer has a multiple quantum well structure, the frequency characteristics are improved while light absorption is reduced.

According to a method of manufacturing a modulator integrated type semiconductor laser device according to the present invention, a first waveguide layer having an active layer on one principal surface of a semiconductor substrate of a first conductivity type and the first waveguide A first cladding layer of a second conductivity type semiconductor disposed on the layer, and a diffraction grating is embedded between the first cladding layer or the semiconductor substrate and the first waveguide layer. A first step of preparing a laminated structure further comprising a second cladding layer of a semiconductor of a predetermined conductivity type, and on the surface of the first cladding layer, a diffraction grating extending in the laser waveguide direction. A second step of forming a striped first dielectric film having the entire length overlapping the semiconductor substrate and partially etching the semiconductor substrate using the first dielectric film as a mask until the semiconductor substrate is exposed; and Using one dielectric film as a mask, the band gap is larger than that of the active layer. A third step of sequentially forming a second waveguide layer having an optical waveguide layer having a large energy and a third cladding layer of the second conductivity type semiconductor on the semiconductor substrate exposed by etching; The film is removed, and on the surfaces of the second cladding layer and the third cladding layer, a second dielectric film in a stripe shape including the position of the first dielectric film and further extending in the laser waveguide direction. A fourth step of etching until the semiconductor substrate is exposed using this second dielectric film as a mask, and using the second dielectric film as a mask,
The third waveguide layer having a semiconductor light absorbing layer larger than the band gap energy of the active layer and smaller than the band gap energy of the optical waveguide layer and the fourth cladding layer of the second conductivity type semiconductor were exposed by etching. The fifth step of sequentially forming on the semiconductor substrate, the second dielectric film is removed, the second clad layer, the third clad layer and the fourth clad layer on the surface of the second dielectric A stripe-shaped third dielectric film including the film position and extending in the laser waveguide direction is formed, and etching is performed using the third dielectric film as a mask until the semiconductor substrate is exposed to form a ridge. And a sixth step of forming a current blocking layer on the semiconductor substrate exposed by etching, so that the first, second and third waveguide layers can be individually formed by crystal growth. Number properties improved the modulator-integrated semiconductor laser device of high degree of freedom in design can be easily formed.

A first waveguide layer having an active layer and a second conductivity type semiconductor disposed on the first waveguide layer are formed on one main surface of a semiconductor substrate of the first conductivity type. A first cladding layer is disposed, and a second cladding layer of a predetermined conductivity type semiconductor having a diffraction grating embedded therein is provided between the first cladding layer or the semiconductor substrate and the first waveguide layer. A first step of preparing a laminated structure further provided, and a stripe shape on the surface of the first cladding layer, which extends in the laser waveguide direction, overlaps the diffraction grating, and has a partial length of the semiconductor substrate as a whole. The first dielectric film and a portion including an end portion which is opposed to each other via a stripe portion on the extension of the first dielectric film in the laser waveguide direction and which is close to the first dielectric film are other portions. A pair of narrower second dielectric films is formed, and these dielectric films are used as a mask to form a half. A second step of the body substrate is etched until exposing the first, the second dielectric film as a mask,
Forming a second waveguide layer having a semiconductor layer having a larger band gap energy than the active layer and a third cladding layer of the second conductivity type semiconductor by selective growth on the semiconductor substrate exposed by etching; Removing the first and second dielectric films, including the position of the second dielectric film on the surfaces of the second cladding layer and the third cladding layer, and further extending in the laser waveguide direction. Forming a striped third dielectric film, etching using the third dielectric film as a mask until the semiconductor substrate is exposed to form a ridge, and forming a current blocking layer on the semiconductor substrate exposed by the etching. And the waveguide of the modulator region can be formed at a time, so that the process can be simplified.

Further, on one principal surface of the semiconductor substrate of the first conductivity type, they face each other via a stripe shape extending in the waveguide direction of the laser and extending over a part of the length of the semiconductor substrate. A part including one end in the waveguide direction forms a pair of first dielectric films having a shape narrower than the other part, and the band gap energy is smaller than that of the semiconductor substrate using the first dielectric film as a mask. A first step of forming a first waveguide layer having a first semiconductor layer by selective growth, and removing the first dielectric film, formed between a pair of first dielectric films. A second dielectric film having a stripe shape corresponding to the length of the first dielectric film is formed at a position on the surface of the first waveguide layer, and a semiconductor is formed using the second dielectric film as a mask. A second step of etching until the substrate is exposed, and a mask of the second dielectric film A third step of forming a second waveguide layer having a semiconductor active layer having a smaller bandgap energy than the first semiconductor layer by selective growth on the semiconductor substrate exposed by etching; and The dielectric film is removed, a first cladding layer of the second conductivity type semiconductor and a light guide layer of the second conductivity type semiconductor are sequentially formed on the first and second waveguide layers, and the light guide layer is etched. Forming a diffraction grating facing the active layer, and embedding the diffraction grating with a second cladding layer of a second conductivity type semiconductor; and a second dielectric layer on the second cladding layer. Forming a striped third dielectric film extending in the laser waveguide direction with a width equal to or less than the width of the film and covering the first semiconductor layer and the active layer; and forming the third dielectric film. Using the mask as a mask, etch until the semiconductor substrate is exposed to form a ridge. Because it includes a fifth step of forming a current blocking layer on a semiconductor substrate which is exposed by etching, and since the waveguide of the modulator section and the isolation region can be formed at one time, it is possible to simplify the process.

Further, the first conductive type semiconductor substrate is provided on one principal surface of the first conductive type semiconductor substrate via a diffraction grating extending in the laser waveguide direction and having a part of the length of the semiconductor substrate as a whole. A first step of preparing a laminated structure in which a first cladding layer of a semiconductor is provided, and on a surface of the first cladding layer, via a stripe portion extending from the tip of the diffraction grating in the laser waveguide direction. A part including the end part which is opposed to each other and is close to the diffraction grating forms a pair of first dielectric films which are narrower than the other part, and the first dielectric film is used as a mask to form a pair of first dielectric films. A second step of forming a first waveguide layer having a semiconductor active layer having a small band gap energy by selective growth on a semiconductor substrate exposed by etching, and on the surface of the first waveguide layer, This first dielectric film is located between the pair of first dielectric films. A second step of forming a second dielectric film in a stripe shape corresponding to the length, etching using the second dielectric film as a mask until the first clad layer is exposed, A third step of forming a second waveguide layer having a semiconductor active layer having a band gap energy smaller than that of the first semiconductor layer using the film as a mask on the semiconductor substrate by selective growth; Removing the film and forming a second cladding layer on the first and second waveguide layers; and forming a laser on the second cladding layer with a width equal to or less than the width of the second dielectric film. A stripe-shaped third dielectric film extending in the waveguide direction and having a length covering the first semiconductor layer and the active layer is formed, and the third dielectric film is used as a mask until the semiconductor substrate is exposed. Etching to form a ridge and exposing the semiconductor substrate And a fifth step of forming a current block layer thereon, so that in a configuration having a diffraction grating on the substrate side, the separation region and the waveguide of the modulator section can be formed at once, thereby simplifying the steps. It can be carried out.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a partially cutaway perspective view of a semiconductor laser with a modulator according to one embodiment of the present invention. FIG. 2 shows II- of FIG.
It is sectional drawing of II cross section. Here, a semiconductor laser with a modulator of 10 Gb / s used for trunk communication will be described as an example. This semiconductor laser with a modulator is a composite optical device in which an electroabsorption external modulator and a single-wavelength laser are integrated.

1 and 2, reference numeral 10 denotes a laser with a modulator, part A denotes a modulator part, part B denotes a separation part, and part C denotes a laser part. 1 and 2, reference numeral 12 denotes an n-InP substrate, and reference numeral 14 denotes a stripe-shaped n-InGaAsP laser n-side optical confinement layer disposed at a portion C at one end of the substrate 12. In the following description of materials including n-InGaAsP, the description of InGaAsP means an InGaAsP-based material having a predetermined composition ratio.

Reference numeral 16 denotes an active layer of InGaAsP-MQW laminated on the laser n-side optical confinement layer 14, 18 denotes a laser p-side optical confinement layer of p-InGaAsP laminated on the active layer 16, The laser n-side optical confinement layer 14, the active layer 16, and the laser p-side optical confinement layer 18 are stacked in a ridge shape to form a laser waveguide 20 as a first waveguide.

22c is a first cladding layer of p-InP,
It is arranged on the laser waveguide 20. 24 is p-In
A GaAsP diffraction grating is buried in the first cladding layer 22c so as to face the active layer 16. Reference numeral 26 denotes a second cladding layer of p-InP, which is disposed on the first cladding layer 22 (22a, 22b and 22c) so as to cover the entire surface of the modulator section A, the separation section B and the laser section C. 28 is p ⁺ -InGa
The contact layer of As is provided on the second cladding layer 26 of the modulator section A and the laser section C excluding the separation section B.

Numeral 30 denotes an n-InGaAsP separating portion n-side optical confinement layer provided on the substrate 12 of the separating portion B, and 32 denotes an optical waveguide disposed on the separating portion n-side optical confinement layer 30. Each of the layers has a bulk structure of InGaAsP made of a material having a larger band gap energy than that of the active layer 16. The bulk structure may be a bulk crystal structure formed by recrystallization growth or a so-called bulk-like structure in which InGaAsP-MQW is mixed and crystallized by performing ion implantation. 3
4 is a p-InGaAsP disposed on the optical waveguide layer 32
Is a light confinement layer on the p-side of the separation part. Reference numeral 22b denotes a first cladding layer provided on the light confinement layer 34 on the separation portion p side.

The separation portion n-side light confinement layer 30, the optical waveguide layer 32, and the separation portion p-side light confinement layer 34 are stacked in a ridge shape to form the second
Is formed, and is connected to the laser waveguide 20 so as to extend in the light emission direction. When the separation portion n-side optical confinement layer 30, the optical waveguide layer 32, and the separation portion p-side optical confinement layer 34 are formed by regrowth, the active layer 16 is included via a bonding surface that is a regrowth interface. The laser waveguide 20 and the separation waveguide 36 including the optical waveguide layer 32 are connected, but the optical waveguide layer 32 and the light absorption layer 40 are formed simultaneously with the active layer 16 in the MQW structure to form a bulk structure by mixed crystal formation. In this case, there is no bonding surface which is a regrowth interface.

Numeral 38 denotes an n-InGaAsP modulator section n-side optical confinement layer disposed on the substrate 12 of the modulator section A, and 40 denotes a modulator section disposed on the n-side optical confinement layer 38. Light absorbing layer, 4
2 is a p-InGaAsP disposed on the light absorption layer 40
Modulator side p-side light confinement layer. The light absorbing layer 40 has a bulk structure made of InGaAsP, which is a material having a larger band gap energy than the active layer 16 and a smaller band gap energy than the optical waveguide layer 32 of the separation part B.

The bulk structure may be a bulk crystal structure formed by recrystallization growth or a so-called bulk-like structure in which InGaAsP-MQW is mixed and crystallized by ion implantation. Reference numeral 22a denotes a first cladding layer of p-InP disposed on the modulator side p-side optical confinement layer 34.

Modulator section n-side light confinement layer 38, light absorption layer 40
The modulator section p-side optical confinement layer 42 is laminated in a ridge shape to form a modulator section waveguide 44 as a third waveguide, and is connected to the laser waveguide 20 in the extension of the light emitting direction. . When the modulator portion n-side light confinement layer 38, the light absorption layer 40, and the modulator portion p-side light confinement layer 42 are formed by regrowth, the modulator portion is guided through a bonding surface which is a regrowth interface. The waveguide 44 is connected to the separation part waveguide 36. However, when the bulk structure is formed by the mixed crystal of MQW, there is no bonding surface which is a regrowth interface.

46 is a first buried layer of Fe-doped InP, 4
Reference numeral 8 denotes an n-InP hole trapping layer provided on the first burying layer 46, 50 denotes a second burying layer of Fe-doped InP provided on the hole trapping layer 48, and 46,
The hole trap layer 48 and the second buried layer 50 constitute a window structure 52 on the emission end face side.

The first buried layer 46, the hole trap layer 48, and the second buried layer 50 are provided on the laser waveguide 20, the separation section waveguide 36, the modulator section waveguide 44, and these waveguides. The buried first cladding layer 22 is also buried on both side surfaces of the ridge.
6. The hole trap layer 48 and the second buried layer 50 constitute a current blocking layer 54.

Reference numeral 56 denotes an SiO2 insulating film which is formed on the entire surface of the contact layer 28, with openings provided at necessary places. Reference numeral 58 denotes a separation groove for separating the laser section C and the modulator section A, and this section is dug into the second cladding layer 26 by removing the contact layer 28. Reference numeral 60 denotes a Ti / Au surface-deposited electrode formed at the opening of the insulating film 56. 62 is a p-side laser electrode of an Au plating layer as a first electrode, 64 is a p-side modulator electrode of an Au plating layer as a second electrode, 66
Reference numeral 68 denotes a deposition electrode laminated on the back surface of the substrate in a layer sequence of AuGe / Ni / Ti / Pt / Ti / Pt / Au, and a common electrode of an Au plating layer 68 as a third electrode. The arrow 70 indicates the emission direction of the laser beam.

FIG. 3 shows an active layer 1 of InGaAsP-MQW.
6 is a sectional view of FIG. Reference numeral 16a is a well layer having a thickness of 3 to 4 nm and a number of layers of 7 to 13 layers. A barrier layer 16b is formed between the well layers 16a. The layer thickness of the barrier layer 16b is 1
It is about 0 nm. The well layer 16a and the barrier layer 16b are both formed of undoped InGaAsP.
a is In having a smaller band gap than the barrier layer 16b.
It is made of GaAsP.

The laser with modulator according to the present invention is manufactured as follows. FIGS. 4, 5, 7, 8, 9 and 10 are cross-sectional views of an element showing a manufacturing process of the laser with modulator according to the present invention. FIG. 6 is a perspective view of an element in a partial process. First, referring to FIG. 4, M-InP
By the OCVD method, n as the laser n-side optical confinement layer 14
-InGaAsP layer, InGaAs as active layer 16
P-I as a P-MQW layer and a laser p-side optical confinement layer 18
nGaAsP layer, p-InP layer as a part of the first cladding layer 22c, and pI for forming the diffraction grating 24
An nGaAsP layer is sequentially stacked. The result of this step is shown in FIG.
(A).

Next, in order to form the diffraction grating 24, p
-The InGaAsP layer is etched into a lattice shape by using the interference exposure method to form the diffraction grating 24. Thereafter, to embed the diffraction grating 24, a p-InP layer as the first cladding layer 22c is grown on the entire surface. The result of this step is shown in FIG.
(B). P-I as the first cladding layer 22
A dielectric film such as SiO2 or SiN is formed on the nP layer, and the dielectric film is etched so as to overlap the diffraction grating 24 and leave a stripe-shaped dielectric film 72 for forming the laser waveguide 20. This striped dielectric film 7
Using the mask 2 as a mask, the lamination in the region including the separation section B and the modulator section A is etched until the substrate 12 is exposed. FIG. 5A shows the result of this step. FIG. 6 shows FIG.
3 is a perspective view of the element shown in FIG.

Next, while leaving the striped dielectric film 72, the substrate 12 exposed by etching is
By MOCVD, an n-InGaAsP layer as an isolation part n-side optical confinement layer 30, an undoped InGaAsP layer as an optical waveguide layer 32, a p-InGaAsP layer as an isolation part p-side optical confinement layer 34, and a first cladding layer A p-InP layer as 22b is sequentially stacked. The InGaAsP layer serving as the optical waveguide layer 32 has a bulk crystal structure formed to have a band gap energy larger than that of the active layer 16. FIG. 5B shows the result of this step.

Next, the striped dielectric film 72 is removed from the mask, and a dielectric film such as SiO 2 or SiN is formed on the p-InP layers as the first cladding layers 22b and 22c. 20 and separation part waveguide 36
Is formed, a dielectric film 74 in the form of a stripe is formed, which overlaps the diffraction grating 24 and extends further toward the emission end face, and the dielectric film 74 is used as a mask to laminate the region including the modulator section A to the substrate. Etch until 12 is exposed. FIG. 7A shows the result of this step.

Next, while leaving the dielectric film 74 in the form of stripes, the substrate 12 exposed by etching is
By the MOCVD method, an n-InGaAsP layer as a modulator part n-side light confinement layer 38, an undoped InGaAsP layer as a light absorption layer 40, a p-InGaAsP layer as a modulator part p-side light confinement layer 42, and a first Cladding layer 22a
Are sequentially laminated. Light absorbing layer 40
Is a bulk crystal structure made of a material having a larger band gap energy than the active layer 16 and a smaller band gap energy than the optical waveguide layer 32 of the separation part B. FIG. 7B shows the result of this step.

Next, in FIG. 8, the dielectric film 74 is removed, and the first cladding layer 22 (22a, 22b and 22c) is removed.
A dielectric film such as SiO2 or SiN is formed again on the p-InP layer of FIG.
0, a striped dielectric film 76 for forming the separation section waveguide 36 including the optical waveguide layer 32 and the modulator section waveguide 44 including the light absorption layer 40 is formed (FIG. 8A). Using the dielectric film 76 as a mask, until the substrate 12 is exposed.
Ridge formation as a waveguide is performed by performing wet etching using Hbr. At this time, when forming the window structure on the emission end face, etching is performed not only on both side faces of the waveguide but also near the emission end face until the substrate 12 is exposed. FIG. 8B shows the result of this step. FIG. 8B shows FIG.
It is a sectional view of an element in a position of a VIIIB-VIIIB section of (a).

Next, with the dielectric film 76 left as a mask, an Fe-doped InP layer as the first buried layer 46, an n-InP layer as the hole trap layer 48, and an Fe-doped InP layer as the second buried layer 50 InP is sequentially laminated by MOCVD. FIG. 9A shows the result of this step. FIG. 9A is a cross-sectional view of the element at the position of the VIIIB-VIIIB cross section in FIG.

Next, the p-type as the second cladding layer 26 is formed on the entire surface of the first cladding layer 22 and the second burying layer 50.
P ⁺ -InGa as InP layer and contact layer 28
Crystal growth of the As layer is sequentially performed by the MOCVD method. FIG. 9B shows the result of this step. Next, a part of the contact layer 28 and the second cladding layer 26 corresponding to the separation part B is removed by etching to form a separation groove 58. At this time, a tartaric acid solution is used for etching the p ⁺ -InGaAs layer serving as the contact layer 28, and hydrochloric acid is used for etching the p-InP layer of the second cladding layer 26. The result of this step is shown in FIG.
It is.

Thereafter, an insulating film 56 such as SiO 2 is formed on the entire surface including the surface of the separation groove 58 by sputtering, an opening is provided in an electrode contact portion, the insulating film 56 is removed, and a surface deposition electrode is formed on the electrode portion. Ti / Au as 60
A film is formed by vapor deposition, and an Au plating layer is formed thereon,
A p-side laser electrode 62 and a p-side modulator electrode 64 are formed. On the back side of the device, the back surface of the substrate is
Grind to about 0 μm, AuGe / Ni / Ti /
A deposition electrode 66 is laminated on the back surface of the substrate in a layer sequence of Pt / Ti / Pt / Au, an Au plating layer is formed thereon, and a common electrode 68 is formed, thereby completing the semiconductor laser 10 with a modulator.

In the above manufacturing method, the case where the bulk crystal growth is performed by using the butt joint method in forming the separation section waveguide 36 and the modulator section waveguide 44 has been described. And the optical waveguide layer 32 and the light absorption layer 40 may both be formed as MQW structures. In such a butt joint method, since the laser section C, the separation section B, and the modulator section A can be formed of different materials and layer structures, the degree of design freedom is high, and the laser section C, the separation section B, and the modulator section A can be formed into a structure having a refractive index and a band gap energy suitable for each of A.

After the step shown in FIG. 5A, the substrate 12 is then removed while leaving the dielectric film 72 in the form of stripes.
Above, when the optical waveguide layer 32 is formed by MOCVD, InGaAsP-MQW is formed, and the optical waveguide layer 32 of the separation part B and the light absorption layer 40 of the modulator part A are mixed with each other by a degree of mixed crystal formation by ion implantation. By changing, the band gap energy of the optical waveguide layer 32 may be made larger than the band gap energy of the light absorption layer 40. FIG. 11 is a cross-sectional view of the element in a step showing ion implantation. Here, the length of the arrow indicates the magnitude of the dose.

In FIG. 11, reference numeral 78 denotes an optical waveguide layer having an MQW structure mixed by ion implantation, and reference numeral 80 denotes a light absorption layer having an MQW structure mixed by ion implantation. In this case, the active layer 16 and the optical waveguide layer 78 are connected by a butt joint, and the optical waveguide layer 78 and the optical absorption layer 8 are connected.
0 becomes a so-called bulk-like structure. The ion species are Si, Zn, and InGaAsP-MQW.
Ga or the like can be used. In the case of InGaAlAs-MQW, Si, Zn, Ga, Al or the like can be used.

FIG. 12 is a cross-sectional view of an element formed by changing the degree of mixed crystal formation by ion implantation. The configuration is the same as that of FIG. 2 except that the optical waveguide layer 78 of the separation section B and the light absorption layer 80 of the modulator section A are different. Further, after forming the MQW active layer 16 of FIG. 4A or FIG. 4B, the optical waveguide layer 32 of the separation part B and the light absorption layer 40 of the modulator part A are mixed crystallized by ion implantation. By changing the degree, the bandgap energy of the light absorbing layer 40 can be larger than that of the light guiding layer 3.
2 may be formed so as to increase the band gap energy. In this case, the butt joint is not included.

Next, the operation of the semiconductor laser with modulator according to the present invention will be described. Laser electrode 62 and common electrode 6
8, a current is injected into the active layer 16 by applying a forward bias voltage, and the laser light emitted by the laser section C is guided to the modulator section waveguide 44 via the separation section waveguide 36. At this time,
A modulation signal of a reverse bias voltage is applied between the modulator electrode 64 and the common electrode 68, and an electric field corresponding to the modulation signal is applied to the light absorption layer 40, thereby emitting the laser light 70 modulated at high speed. Things. At this time, since the light absorption layer 40 has a bulk crystal structure or a mixed crystal bulk structure, the modulation principle is not the quantum confined Stark effect,
Franz Keldish effect.

In the Franz-Keldysh effect, the change in the absorption coefficient due to the electric field is small, and the change in the refractive index due to the change in the absorption coefficient is small. Therefore, by using a bulk type modulator, wavelength fluctuation due to a change in refractive index can be reduced, which is advantageous for long-distance transmission.

Further, since the optical waveguide layer 32 of the separation portion has a bulk crystal structure or a bulk structure which is a mixed crystal-like bulk, the change in the absorption coefficient due to the electric field is small in the Franz-Keldysh effect. Even if a leakage electric field is applied to the optical waveguide layer 32, the change in the amount of light absorption can be reduced. In particular, since the optical waveguide layer 32 of the separation portion responds only to a low frequency (several Ghz), the frequency characteristic does not become flat when the amount of light absorption changes, but the frequency characteristic is deteriorated by forming the optical waveguide layer 32 into a bulk structure. Can be reduced.

Further, by forming the optical waveguide layer 32 and the light absorbing layer 40 into a bulk crystal structure by recrystallization by the butt joint method, a semiconductor laser with a modulator having a small light absorption due to a small number of non-emitting coupling centers is formed. can do. In the configuration described above, the diffraction grating is p-InP
Although the configuration is provided in the layer, the diffraction grating may be provided on the substrate side.

FIG. 13 is a sectional view showing an example of a modification of the first embodiment. In FIG. 13, the diffraction grating 24 is embedded in a third cladding layer 82 of n-InP, and the third cladding layer 82 is formed by the laser n-side optical confinement layer 14, the separation unit n-side optical confinement layer 30, and the modulator. It is disposed between the portion n-side light confinement layer 38 and the substrate 12. FIG. 14 is a sectional view showing another modification of the first embodiment. In FIG. 14, the diffraction grating 24 is formed by being embedded in the substrate 12,
A third cladding layer 82 of n-InP is provided thereon,
The laser n-side optical confinement layer 1 is interposed via the third cladding layer 82.
4. The separation part n-side light confinement layer 30 and the modulator part n-side light confinement layer 38 are provided.

Embodiment 2 In this embodiment 2, when the separation section waveguide 36 and the modulator section waveguide 44 are simultaneously formed by recrystallization growth using a butt joint method, light is absorbed by the band gap energy of the active layer 16. In order to increase the band gap energy of the layer 40 and further increase the band gap energy of the optical waveguide layer 32 compared to the light absorption layer 40, the separation waveguide 36 including the optical waveguide layer 32 and the light absorption layer 40 are selectively grown. The thickness of the layer of the modulator section waveguide 44 is changed.

Example 1 FIG. 15 is a sectional view of a semiconductor laser with a modulator of Example 1 according to the second embodiment. In FIG. 15, reference numeral 90 denotes a semiconductor laser with a modulator. 2 denote the same or corresponding parts. In the semiconductor laser 90 with a modulator, the separation section waveguide 36 and the modulator section waveguide 4
4, the separation part n-side light confinement layer 30 and the modulator part n-side light confinement layer 38, the optical waveguide layer 32 and the light absorption layer 40, and the separation part p-side light confinement layer 34 and the modulator part p side Each of the optical confinement layers 42 has a bulk crystal structure formed simultaneously by selective growth.

The thickness of each layer of the separation section waveguide 36 is thinner on the side of the laser waveguide 20 and thicker on the side of the modulator section waveguide 44. The separation section waveguide 36 and the laser waveguide 20 are connected to each other so that the thicknesses of the respective layers are the same via the bonding surface of the recrystallization interface. Next, a method of manufacturing the semiconductor laser with modulator 90 according to the second embodiment will be described. FIG.
6, FIG. 18 is a cross-sectional view of the element showing each step, and FIG. 17 is a perspective view of the element showing one step.

In FIG. 16, first, an n-InP substrate 1
An n-InGaAsP layer as a laser n-side optical confinement layer 14, an undoped InGaAsP-MQW layer as an active layer 16, and a p-InGaAsP layer as a laser p-side optical confinement layer 18 are sequentially stacked on the substrate 2 by MOCVD. An insulating film 92 such as SiO2 or SiN is formed on the surface. FIG. 16 shows the result of this step.

Next, as shown in FIG. 17, the insulating film 92 is subjected to a photolithography process and an etching process to form the laser waveguide 2.
0, and a stripe shape is set on the laser emission end face side of the insulation film 94, and a trapezoidal shape extending on both longitudinal sides of the stripe shape through the stripe shape. Are formed. The width of the trapezoid is narrow on the side close to the insulating film 94 and gradually increases as the distance from the insulating film 94 increases, and becomes uniform from a predetermined position. The portion where the width changes corresponds to the separation portion waveguide 36. Using the insulating films 94 and 96 as a mask, etching is performed until the substrate 12 is exposed. FIG. 17 shows the result of this step.

Next, with the insulating film 94 and the insulating film 96 left as a mask, selective growth by MOCVD is performed.
An n-InGaAsP layer as the separation unit n-side light confinement layer 30 and the modulator unit n-side light confinement layer 38, an InGaAsP layer as the light guide layer 32 and the light absorption layer 40, and a separation unit p-side light confinement layer 34 And p-I as the p-side optical confinement layer 42 of the modulator section
An nGaAsP layer is sequentially stacked. As a result of this selective growth, in the stripe-shaped portion sandwiched between the pair of insulating films 96, the thickness of the stack changed as the width of the insulating film 96 gradually increased, and the width of the insulating film 96 became uniform. Incidentally, the layers are stacked so that the thickness of the layers is constant. FIG. 18A shows the result of this step. FIG. 18 (a) shows the XV of FIG.
It is a cross section at the IIIA-XVIIIA position.

Next, the insulating films 94 and 96 are removed,
The first cladding layer 22 is formed on the laser part p-side light confinement layer 18, the separation part p-side light confinement layer 34, and the modulator part p-side light confinement layer 42.
A p-InP layer as the active layer 1 of the laser section C
6, a diffraction grating 24 is formed, and then the diffraction grating 24 is embedded with a p-InP layer as the first cladding layer 22. FIG. 18B shows the result of this step. Next, a ridge is formed on the waveguide. In the subsequent manufacturing steps, an element is formed according to the steps described in the first embodiment.

Another Modification of the Manufacturing Method of Embodiment 1 Another modification of the manufacturing method of forming the separation section waveguide 36 and the modulator section waveguide 44 by selective growth using a butt joint method will be described. 19 and 21 are perspective views showing the device in one process, and FIGS. 20 and 22 are cross-sectional views of the device showing the manufacturing process.

First, in FIG. 19, a selective growth mask for forming the separation section waveguide 36 and the modulator section waveguide 44 on the substrate 12 is formed. That is, an insulating film is formed on the substrate 12, and a stripe shape corresponding to the waveguide shape of the output end face side separation portion waveguide 36 and the modulator portion waveguide 44 is set. A pair of trapezoidal insulating films 96 extending on both side surfaces are formed by photolithography and etching. This insulating film 96 has a trapezoidal width narrower on the inner side of the substrate 12 and gradually becomes wider and uniform as approaching the emission end face. The portion where the width changes corresponds to the separation portion waveguide 36. FIG. 19 shows the result of this step.

Next, referring to FIG. 20, the insulating film 96 is used as a selective growth mask, and the n-type optical confinement layer 30 and the modulator n-side optical confinement layer 38 are formed by MOCVD using the MOCVD method.
InGaAsP layer, InGaAsP layer as optical waveguide layer 32 and light absorption layer 40, and p-InGaAsP as separation part p-side light confinement layer 34 and modulator part p-side light confinement layer 42
The layers are sequentially stacked. By this selective growth, a pair of insulating films 9 are formed.
6, the thickness of the layer is constant where the width of the insulating film 96 on the emission end face side is uniform.
The lamination is performed so that the thickness of the lamination becomes thinner as the width of the insulating film 96 gradually decreases from the place where the width of the insulating film 96 is uniform toward the inside of the substrate 12. FIG. 20A shows the result of this step.

Next, the insulating film 96 is removed, an insulating film is formed anew, and a photolithography process and etching are performed so that the stripe-shaped portion sandwiched between the pair of insulating films 96 has a width smaller than this portion. A striped insulating film 98 having the same length as the insulating film 96 is formed (FIG. 20B), and the insulating film 98 is used as a mask to leave the separating portion waveguide 36 and the modulator portion waveguide 44. Etch until 12 is exposed. FIG. 20C shows the result of this step. FIG. 21 is a perspective view of the element in this step.

Next, while the insulating film 98 is left as a mask, n-InGaAs as the laser n-side optical confinement layer 14 is used.
A P layer, an InGaAsP-MQW layer as the active layer 16,
A p-InGaAsP layer as a laser p-side optical confinement layer 18 is sequentially laminated on the substrate 12. The result of this step is shown in FIG.
(A). Thereafter, the insulating film 98 is removed, and the separating portion p
Side optical confinement layer 34, modulator section p side optical confinement layer 42 and laser p
A p-InP layer as the first cladding layer 22 is formed on the surface of the side light confinement layer 18, and a diffraction grating 24 is formed corresponding to the active layer of the laser section C. The result of this step is shown in FIG.
(B). FIG. 22 is a cross-sectional view taken along a line XXII-XXII in FIG. Next, the diffraction grating 24 is embedded in the first cladding layer 22 to form a ridge of the waveguide.
In the subsequent manufacturing steps, an element is formed according to the steps described in the first embodiment.

Example 2 In the above description of the second embodiment, the diffraction grating 24 is provided on the p-InP layer. However, the diffraction grating 24 is provided on the n-InP layer on the substrate side. Is also good. FIG.
FIG. 7 is a cross-sectional view showing Example 2 of Embodiment 2. In FIG. 23, a diffraction grating 24 is embedded in a third cladding layer 82 of n-InP, and this third cladding layer 82 is composed of a laser n-side light confinement layer 14, a separation part n-side light confinement layer 30, and a modulator. It is disposed between the portion n-side light confinement layer 38 and the substrate 12. FIG. 24 is a sectional view showing another modification of the second embodiment. In FIG. 24, the diffraction grating 24 is formed by being embedded in the substrate 12, and a third cladding layer 82 of n-InP is provided thereon, and the laser n-side light confinement is performed via the third cladding layer 82. The layer 14, the separation part n-side light confinement layer 30, and the modulator part n-side light confinement layer 38 are provided.

The manufacturing method according to the second embodiment shown in FIG. 23 will be described. FIG. 25 is a cross-sectional view of the device showing a manufacturing process. First, in FIG. 25, a diffraction grating 24 is formed on the end face side on which the laser waveguide 20 is formed on the substrate 12, and this diffraction grating 2
4 is buried with an n-InP layer as a third cladding layer 82. Thereafter, by the same manufacturing method as the modification of the manufacturing method of the first embodiment, the MOCVD method using a selective growth mask is used to form the separation portion n-side light confinement layer 30 and the modulator portion n-side light confinement layer 38. The n-InGaAsP layer, the InGaAsP layer as the optical waveguide layer 32 and the light absorption layer 40, and the p-type as the p-side light confinement layer 34 and the p-side light confinement layer 42 for the modulator part and the p-side light confinement layer 42 for the modulator part.
InGaAsP layers are sequentially stacked. FIG. 25A shows this result.

Next, the insulating film 96 is removed, an insulating film is newly formed, and a photolithography process and etching are performed to form a stripe-shaped portion sandwiched between the pair of insulating films 96 with a width smaller than this portion. A stripe-shaped insulating film 98 having the same length as the above-mentioned insulating film 96 is formed (see FIG. 25B), and the insulating film 98 is used as a mask to leave the separating portion waveguide 36 and the modulator portion waveguide 44 and to be etched. At this time, in the modification of the manufacturing method of the first embodiment, the etching is performed until the substrate 12 is exposed.
4 is formed on the substrate 12, and stops when the n-InP layer as the third cladding layer 82 is exposed (FIG. 26A). Next, while the insulating film 98 is left as a mask, the n-In
N-In as a laser n-side optical confinement layer 14 on the P layer
GaAsP layer, InGaAsP-M as active layer 16
P-I as QW layer and laser p-side optical confinement layer 18
The nGaAsP layer is formed as n-I as the third cladding layer 82.
The layers are sequentially stacked on the nP layer.

After that, the insulating film 98 is removed, and the first cladding is formed on the surfaces of the separation part p-side light confinement layer 34, the modulator part p-side light confinement layer 42, and the laser p-side light confinement layer 18. A p-InP layer is formed as the layer 22 (FIG. 26B). In the subsequent manufacturing steps, an element is formed according to the steps described in the first embodiment. In the semiconductor laser 90 with a modulator configured as described above, the separation section waveguide 36 and the modulator section waveguide 44 are simultaneously formed by recrystallization growth by the butt joint method, so that the optical waveguide layer 32 and the light absorption layer 40 are formed. Has a bulk crystal structure, the modulator has a small change in the absorption coefficient due to the electric field, and a small change in the refractive index due to the change in the absorption coefficient. It can be. Further, by forming the optical waveguide layer 32 of the separation part B into a bulk crystal structure,
Since the change in the absorption coefficient due to the electric field is small, the change in the amount of light absorption can be reduced even if there is a leakage electric field,
Deterioration of frequency characteristics at low frequencies (several GHz) can be reduced.

Further, while simultaneously forming the separation section waveguide 36 and the modulator section waveguide 44 by selective growth, the thickness of the layer of the separation section waveguide 36 is reduced on the side of the laser waveguide layer 20, and the modulator section waveguide 44 is formed. By increasing the thickness on the side, the bandgap energy of the optical waveguide layer 32 is made larger than the bandgap energy of the light absorption layer 40, so that light absorption can be reduced and frequency fluctuation can be reduced.

Further, since the layers of the separation section waveguide 36 and the modulator section waveguide 44 can be formed simultaneously by selective growth, the number of manufacturing steps can be reduced and the formation can be simplified. In the above description, the configuration in which the optical waveguide layer 32 and the light absorption layer 40 have a bulk crystal structure has been described.
The optical waveguide layer 32 and the light absorption layer 40 may be made of MQW, mixed with different degrees of ion implantation, and the band gap energy of the optical waveguide layer 32 may be larger than the band gap energy of the light absorption layer 40. Thereby, the optical waveguide layer 32 and the light absorption layer 40 can be easily made into a bulk configuration. In the first and second embodiments, the active layer 16 of the laser section C is made of MQW, but the same effect can be obtained by using a bulk crystal structure.

[0081]

Since the modulator integrated type semiconductor laser device according to the present invention has the structure as described above,
It has the following effects. In the modulator integrated semiconductor laser device according to the present invention, a ridge-shaped first waveguide having an active layer, and an active layer that is continuous with the first waveguide in the extension direction of the first waveguide. A ridge-shaped second waveguide having an optical waveguide layer of a bulk structure having a large bandgap energy, and a bandgap energy of the active layer which is continuous with the second waveguide in the extension direction of the second waveguide. A ridge-shaped third waveguide having a bulk-structured light-absorbing layer that is also larger than the bandgap energy of the optical waveguide layer, and a second conductive layer disposed on the first, second, and third waveguides. Disposed between the first cladding layer or semiconductor substrate of the type semiconductor and the first, second and third waveguides,
A ridge-shaped second cladding layer including a diffraction grating disposed along the first waveguide, and an absorption coefficient that changes due to an electric field variation due to a modulation signal applied to the modulator. Frequency fluctuations, reducing the change in the refractive index of the modulator due to the change in the absorption coefficient, and reducing the light absorption in the optical waveguide layer in the separation region due to the leakage electric field. The modulator integrated semiconductor laser device having improved frequency characteristics can be obtained.

Further, since the second waveguide is continuous with the first waveguide via the joint surface, the frequency characteristics can be improved while keeping the degree of freedom in designing the laser section and the separation region. And the modulator integrated semiconductor laser device with improved frequency characteristics can be obtained.

Further, since the third waveguide is continuous with the second waveguide via the joint surface, and both the optical waveguide layer and the light absorption layer have a bulk crystal structure, light absorption is reduced and frequency characteristics are reduced. And a high output modulator integrated semiconductor laser device can be obtained.

Further, since both the optical waveguide layer and the light absorbing layer have a multi-quantum well structure in which a mixed crystal is formed by disordering, and the degree of the mixed crystal in the optical waveguide layer is higher than that of the absorption layer, the structure is simplified. With such a configuration, it is possible to obtain an inexpensive modulator integrated semiconductor laser device having good frequency characteristics.

Further, since the second waveguide has a larger thickness on the side adjacent to the third waveguide than on the side adjacent to the first waveguide, light absorption is reduced. As a result, the frequency characteristics can be improved, and a modulator-integrated semiconductor laser device with high output can be obtained.

A ridge-shaped first waveguide having an active layer, and a bandgap energy larger than that of the active layer which is continuous with the first waveguide in a direction of extension of the first waveguide via the bonding surface. A ridge-shaped second waveguide having an optical waveguide layer, and an optical waveguide that is continuous with the second waveguide in a direction in which the second waveguide extends and that is larger than the band gap energy of the active layer. A ridge-shaped third waveguide having a light absorption layer having a multiple quantum well structure smaller than the band gap energy of the layer, and a second conductivity type disposed on the first, second and third waveguides. A first cladding layer of a semiconductor, a diffraction layer disposed between the first cladding layer or the semiconductor substrate and the first, second and third waveguides, and disposed along the first waveguide. A ridge-shaped second cladding layer including a lattice, In order to improve the frequency characteristics and reduce the absorption of light by providing a separation region that is less affected by leakage electric field fluctuation due to the modulation signal applied to the modulator, a high-output modulator integrated semiconductor laser with stable frequency This has the effect that the device can be obtained.

Further, since the optical waveguide layer has a bulk crystal structure and the influence of electric field fluctuation due to a modulation signal applied to the modulator is reduced, a modulator integrated semiconductor laser device having good frequency characteristics can be obtained. Having. Further, since the optical waveguide layer has a multiple quantum well structure, it is possible to obtain a modulator integrated semiconductor laser device having good frequency characteristics while reducing light absorption.

In the method of manufacturing a modulator integrated semiconductor laser device according to the present invention, the length of the semiconductor substrate extending on the surface of the first cladding layer in the laser waveguide direction and overlapping the diffraction grating is reduced. A first dielectric film in the form of a stripe having a total length is formed, and etching is performed using the first dielectric film as a mask until the semiconductor substrate is exposed. A second waveguide layer having a large optical waveguide layer with a high gap energy and a third cladding layer of the second conductivity type semiconductor are sequentially formed on the semiconductor substrate exposed by etching, and the first dielectric film is removed. ,
On the surface of the second clad layer and the third clad layer, a second dielectric film of a stripe shape including the position of the first dielectric film and further extending in the laser waveguide direction is formed. Etching is performed until the semiconductor substrate is exposed using the second dielectric film as a mask, and using the second dielectric film as a mask, the light of the semiconductor that is larger than the band gap energy of the active layer and smaller than the band gap energy of the optical waveguide layer. Since the method includes a step of sequentially forming a third waveguide layer having an absorption layer and a fourth cladding layer of the second conductivity type semiconductor on the semiconductor substrate exposed by etching, the first, second and third conductive layers are formed. Since each of the waveguide layers can be individually formed by crystal growth, there is an effect that a modulator integrated semiconductor laser device with improved frequency characteristics can be easily formed with a high degree of design freedom.

On the surface of the first cladding layer, a stripe-shaped first dielectric film extending in the laser waveguide direction, overlapping the diffraction grating and partially extending the entire length of the semiconductor substrate is formed. A pair of second dielectric layers, each including an end portion that is opposed to each other via a stripe portion on the extension in the laser waveguide direction of the first dielectric film and is close to the first dielectric film, is narrower than the other portion. A dielectric film is formed, and etching is performed using the dielectric film as a mask until the semiconductor substrate is exposed. Using the first and second dielectric films as a mask, a semiconductor layer having a larger band gap energy than the active layer is formed. A step of sequentially forming the second waveguide layer and the third cladding layer of the second conductivity type semiconductor on the semiconductor substrate exposed by etching by selective growth, and simultaneously forming the isolation region and the waveguide of the modulator section. Because it can be formed It has the effect of an improved modulator integrated semiconductor laser device having characteristics can be formed by a simple process.

Further, one end in the laser waveguide direction is formed on one main surface of the semiconductor substrate by opposing to each other via a stripe shape extending in the laser waveguide direction and extending over a part of the length of the semiconductor substrate. Forming a pair of first dielectric films, some of which have a narrower width than other portions, and using the first dielectric film as a mask, a first semiconductor layer having a smaller band gap energy than the semiconductor substrate. Is formed by selective growth, the first dielectric film is removed, and a first waveguide layer formed between the pair of first dielectric films is formed on the surface of the first waveguide layer. At a position, a second dielectric film having a stripe shape corresponding to the length of the first dielectric film is formed, and etching is performed until the semiconductor substrate is exposed using the second dielectric film as a mask. Using the dielectric film as a mask, the band gap is larger than that of the first semiconductor layer. A second waveguide layer having an active layer of a semiconductor with low energy is formed by selective growth on the semiconductor substrate exposed by etching, the second dielectric film is removed, and the first and second waveguide layers are removed. Forming a first cladding layer of the second conductivity type semiconductor and a light guide layer of the second conductivity type semiconductor on the first layer, and etching the light guide layer to form a diffraction grating facing the active layer. And the waveguide of the modulator section can be formed at the same time, so that the modulator integrated semiconductor laser device with improved frequency characteristics can be formed by a simple process.

Further, a first conductive type semiconductor substrate is provided on one principal surface of a first conductive type semiconductor substrate via a diffraction grating extending in the laser waveguide direction and having a part of the length of the semiconductor substrate as a whole. A laminated structure in which a first cladding layer of a semiconductor is provided is prepared. On the surface of the first cladding layer, diffraction is performed by opposing each other via a stripe portion extending from the tip of the diffraction grating in the laser waveguide direction. A part including the end part close to the lattice forms a pair of first dielectric films that are narrower than the other part, and the band gap energy of the first semiconductor layer is lower than that of the first semiconductor layer using the first dielectric film as a mask. A first waveguide layer having a small semiconductor active layer is formed by selective growth on a semiconductor substrate exposed by etching, and is sandwiched between a pair of first dielectric films on the surface of the first waveguide layer. Stripes corresponding to the length of this first dielectric film The second dielectric film is formed of, is etched until the second dielectric film as a mask, the first cladding layer to expose the second dielectric film as a mask,
A second waveguide layer having a semiconductor active layer having a smaller bandgap energy than the first semiconductor layer includes a step of forming the semiconductor layer on a semiconductor substrate by selective growth, and in a configuration having a diffraction grating on the substrate side, Since the separation region and the waveguide of the modulator section can be formed at one time, there is an effect that a modulator integrated semiconductor laser device having improved frequency characteristics can be formed by a simple process.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a semiconductor laser with a modulator according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view of an active layer of the MQW.

FIG. 4 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 5 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 6 is a perspective view of an element in a partial process of the laser with a modulator according to the present invention.

FIG. 7 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 8 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 9 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 10 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 11 is a cross-sectional view of the element in a step showing ion implantation of the modulator-equipped laser according to the present invention.

FIG. 12 is a sectional view of a semiconductor laser with a modulator according to the present invention.

FIG. 13 is a sectional view of a semiconductor laser with a modulator according to the present invention.

FIG. 14 is a sectional view of a semiconductor laser with a modulator according to the present invention.

FIG. 15 is a sectional view of a semiconductor laser with a modulator according to the present invention.

FIG. 16 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 17 is a perspective view of an element in a partial process of the laser with a modulator according to the present invention.

FIG. 18 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 19 is a perspective view of an element in a partial process of the laser with a modulator according to the present invention.

FIG. 20 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 21 is a perspective view of an element in a partial process of the laser with a modulator according to the present invention.

FIG. 22 is a cross-sectional view of an element showing a manufacturing process of the laser with a modulator according to the present invention.

FIG. 23 is a sectional view of a semiconductor laser with a modulator according to the present invention.

FIG. 24 is a sectional view of a semiconductor laser with a modulator according to the present invention.

FIG. 25 is a cross-sectional view of an element showing a manufacturing step of the laser with a modulator according to the present invention.

FIG. 26 is a sectional view of an element showing a manufacturing step of the laser with a modulator according to the present invention.

FIG. 27 is a partially cutaway perspective view of a conventional laser with a modulator.

FIG. 28 is a sectional view taken along the line XXVIII-XXVIII in FIG. 27;

[Explanation of symbols]

12 substrate, 16 active layer, 20 laser waveguide, 32 optical waveguide layer, 36 separation section waveguide,
40 light absorption layer, 44 modulator waveguide, 2
2 first cladding layer, 26 second cladding layer,
24 diffraction grating, 54 current blocking layer, 62
p-side laser electrode, 64 p-side modulator electrode, 6
8 Common electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toru Takiguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 2H079 AA02 AA13 BA01 CA04 DA16 DA22 DA25 EA03 EA07 EA08 EB04 HA14 KA18 5F073 AA22 AA45 AA64 AA74 AB21 BA01 CA12 DA05 DA14 DA15 EA14

Claims (12)

[Claims] A first conductive type semiconductor substrate; a ridge-shaped first waveguide provided on a part of one main surface of the semiconductor substrate and having an active layer; A ridge-shaped second optical waveguide layer having a bulk structure with a larger bandgap energy than the active layer is provided on the semiconductor substrate in a direction continuous with the first waveguide in the extension direction of the waveguide. And the second waveguide is disposed on the semiconductor substrate in a direction in which the second waveguide extends, and is larger than the band gap energy of the active layer. A ridge-shaped third waveguide having a light absorption layer having a bulk structure smaller than the band gap energy of the semiconductor layer, and a second conductivity type semiconductor disposed on the first, second and third waveguides The first cladding layer of this A ridge-shaped second layer disposed between the clad layer or the semiconductor substrate and the first, second and third waveguides and including a diffraction grating disposed along the first waveguide. A cladding layer, a current blocking layer disposed on the semiconductor substrate on both sides of the first and second cladding layers, the first, second, and third waveguides; and the first cladding layer. A first electrode disposed on the first cladding layer so as to face the active layer; and a first electrode separated from the first electrode and disposed on the first cladding layer so as to face the light absorption layer. A second electrode, a third electrode disposed on the other main surface of the semiconductor substrate,
Modulator integrated semiconductor laser device comprising: 2. The modulator integrated semiconductor laser device according to claim 1, wherein the second waveguide is continuous with the first waveguide via a joint surface. 3. The modulation according to claim 2, wherein the third waveguide is continuous with the second waveguide via the joint surface, and both the optical waveguide layer and the light absorption layer have a bulk crystal structure. Device integrated semiconductor laser device. 4. An optical waveguide layer and a light absorption layer both having a multiple quantum well structure in which a mixed crystal is formed by disordering.
3. The modulator-integrated semiconductor laser device according to claim 1, wherein the degree of mixed crystal in the optical waveguide layer is higher than that in the absorption layer. 5. The optical waveguide according to claim 2, wherein the optical waveguide layer of the second waveguide has a greater layer thickness on the side adjacent to the third waveguide than on the side adjacent to the first waveguide. Modulator integrated semiconductor laser device. 6. A semiconductor substrate of a first conductivity type; a ridge-shaped first waveguide provided on a part of one main surface of the semiconductor substrate and having an active layer; A ridge-shaped first waveguide having an optical waveguide layer having a band gap energy larger than that of the active layer is provided on the semiconductor substrate so as to be continuous with the first waveguide in the extension direction of the waveguide via the bonding surface. A second waveguide, which is disposed on the semiconductor substrate in a direction in which the second waveguide extends, via the bonding surface with the second waveguide, and which has a band gap energy of A ridge-shaped third waveguide having a light absorption layer of a multiple quantum well structure that is largely smaller than the band gap energy of the optical waveguide layer, and disposed on the first, second, and third waveguides. First cladding of second conductivity type semiconductor And a diffraction grating disposed between the first cladding layer or the semiconductor substrate and the first, second, and third waveguides, and disposed along the first waveguide. A ridge-shaped second cladding layer; the first and second cladding layers; a current blocking layer disposed on the semiconductor substrate on both sides of the first, second and third waveguides; A first electrode disposed on the first cladding layer so as to face the active layer, separated from the first electrode and facing the absorption layer on the first cladding layer; A second electrode provided, a third electrode provided on the other main surface of the semiconductor substrate,
Modulator integrated semiconductor laser device comprising: 7. The modulator integrated semiconductor laser device according to claim 6, wherein the optical waveguide layer has a bulk crystal structure. 8. The modulator integrated semiconductor laser device according to claim 6, wherein the optical waveguide layer has a multiple quantum well structure. 9. A semiconductor substrate of a first conductivity type on one main surface,
A first waveguide layer having an active layer and a first cladding layer of a second conductivity type semiconductor disposed on the first waveguide layer are provided, and the first cladding layer or the semiconductor substrate is provided. A first step of preparing a laminated structure further comprising a second cladding layer of a semiconductor of a predetermined conductivity type in which a diffraction grating is embedded, between the first cladding layer and the first waveguide layer; On the surface of the first dielectric film is formed a stripe-shaped first dielectric film extending in the laser waveguide direction, overlapping the diffraction grating, and partially extending the entire length of the semiconductor substrate. A second step of etching until the semiconductor substrate is exposed as a mask, a second waveguide layer having an optical waveguide layer having a bandgap energy larger than that of the active layer using the first dielectric film as a mask, and a second conductive layer. Etch the third cladding layer of type semiconductor A third step of sequentially forming on the exposed semiconductor substrate, removing the first dielectric film, and positioning the first dielectric film on the surfaces of the second clad layer and the third clad layer. A fourth step of forming a second dielectric film in the form of a stripe extending further in the waveguide direction of the laser and etching the semiconductor substrate using the second dielectric film as a mask until the semiconductor substrate is exposed; The third waveguide layer having a semiconductor light absorption layer larger than the band gap energy of the active layer and smaller than the band gap energy of the optical waveguide layer using the dielectric film of Clad layer,
A fifth step of sequentially forming on the semiconductor substrate exposed by etching, removing the second dielectric film, forming a second clad layer, a third clad layer and a fourth clad layer on the surface of the fourth clad layer; Form a striped third dielectric film including the position of the second dielectric film and extending in the laser waveguide direction, and etching the semiconductor substrate using the third dielectric film as a mask until the semiconductor substrate is exposed. Forming a ridge and forming a current blocking layer on the semiconductor substrate exposed by etching; and a sixth step of manufacturing the modulator integrated semiconductor laser device. 10. A first waveguide layer having an active layer on one principal surface of a semiconductor substrate of the first conductivity type, and a second conductivity type semiconductor disposed on the first waveguide layer. A first cladding layer is provided, and a second cladding layer of a predetermined conductivity type semiconductor having a diffraction grating embedded between the first cladding layer or the semiconductor substrate and the first waveguide layer. A first step of preparing a laminated structure further comprising: a stripe extending on the surface of the first cladding layer in the laser waveguide direction, overlapping the diffraction grating, and having a partial length of the semiconductor substrate as a whole. A first dielectric film and a portion including an end portion which is opposed to each other via a stripe portion extending in the laser waveguide direction of the first dielectric film and which is close to the first dielectric film. Forming a pair of second dielectric films narrower than the portion, and using these dielectric films as a mask. A second step of etching until the conductive substrate is exposed, a second waveguide layer having a semiconductor layer having a band gap energy larger than that of the active layer using the first and second dielectric films as a mask, and a second conductive layer. A third step of sequentially forming a third cladding layer of a type semiconductor on the semiconductor substrate exposed by etching by selective growth, and removing the first and second dielectric films to form a second cladding layer and a second cladding layer. On the surface of the third cladding layer, a stripe-shaped third dielectric film including the position of the second dielectric film and further extending in the laser waveguide direction is formed, and this third dielectric film is masked. Forming a ridge by etching until the semiconductor substrate is exposed, and forming a current blocking layer on the semiconductor substrate exposed by etching. 11. A laser device, comprising: a first conductive type semiconductor substrate, which is opposed to each other via a stripe shape extending in a laser waveguide direction and having a part of the length of the semiconductor substrate as a whole; A part including one end in the waveguide direction forms a pair of first dielectric films having a shape narrower than the other part, and the band gap energy is smaller than that of the semiconductor substrate using the first dielectric film as a mask. A first step of forming a first waveguide layer having a first semiconductor layer by selective growth; and removing the first dielectric film and forming the first waveguide layer sandwiched between a pair of first dielectric films. A second dielectric film having a stripe shape corresponding to the length of the first dielectric film is formed at a position on the surface of the first waveguide layer, and a semiconductor is formed using the second dielectric film as a mask. A second step of etching until the substrate is exposed, and a second dielectric film as a mask. Forming a second waveguide layer having a semiconductor active layer having a smaller band gap energy than the first semiconductor layer by selective growth on the semiconductor substrate exposed by etching; The body film is removed, a first cladding layer of the second conductivity type semiconductor and a light guide layer of the second conductivity type semiconductor are sequentially formed on the first and second waveguide layers, and the light guide layer is etched. Forming a diffraction grating facing the active layer and embedding the diffraction grating with a second cladding layer of a second conductivity type semiconductor; and a second dielectric film on the second cladding layer. A stripe-shaped third dielectric film extending in the laser waveguide direction with a width of not more than the width and covering the first semiconductor layer and the active layer is formed. Etching until the semiconductor substrate is exposed as a mask to form a ridge, A fifth step of forming a current blocking layer on the semiconductor substrate exposed by etching. 12. A semiconductor device of the first conductivity type, which is provided on one principal surface of a semiconductor substrate of the first conductivity type via a diffraction grating that extends in the laser waveguide direction and has a length that is a part of the length of the semiconductor substrate. A first step of preparing a laminated structure provided with a first cladding layer of a semiconductor; and A part including the end part which is opposed to each other and is close to the diffraction grating forms a pair of first dielectric films which are narrower than the other part, and the first dielectric film is used as a mask to form a pair of first dielectric films. A second step of forming a first waveguide layer having a semiconductor active layer having a small bandgap energy by selective growth on a semiconductor substrate exposed by etching, and on the surface of the first waveguide layer, This first dielectric film is positioned between the pair of first dielectric films. Forming a second dielectric film having a stripe shape corresponding to the second dielectric film, etching using the second dielectric film as a mask until the first cladding layer is exposed, a second dielectric film Forming a second waveguide layer having a semiconductor active layer having a smaller bandgap energy than the first semiconductor layer on the semiconductor substrate by using a mask as a mask, and a remaining dielectric film Forming a second cladding layer on the first and second waveguide layers, and guiding the laser over the second cladding layer with a width equal to or less than the width of the second dielectric film. A stripe-shaped third dielectric film extending in the wave direction and having a length covering the first semiconductor layer and the active layer is formed, and etching is performed using the third dielectric film as a mask until the semiconductor substrate is exposed. To form a ridge, and expose the semiconductor substrate exposed by etching. Method for producing a modulator-integrated semiconductor laser device comprising a fifth step of forming a current blocking layer thereon, the.